Skin fibroblasts from human controls or from patients with familial dysautonomia (FD) have been grown in tissue culture. Beta-nerve growth factor has been measured in extracts from both type of cells, using a radioimmunoassay and a bioassay. The FD cells have a 2-3 fold higher content of NGF as measured by RIA than the controls. However, the biological activity of the FD samples is about one-tenth that of the controls when expressed as biological units of activity per ng Beta-NGF as measured in the RIA.